The present invention relates to heat-sensitive image transfer type printing apparatuses and more particularly to a heat-sensitive image transfer type printing apparatus best adapted to record high-quality colored images.
Conventional heat-sensitive image transfer type printing apparatuses are known wherein a record sheet is superposed over a transfer ink film and dyes are transferred from the transfer ink film to the record sheet, thereby obtaining an image recorded sheet. In particular, heat-sensitive colored-image transfer type printing apparatuses utilizing sublimation type ink films ave recently attracted much attention because they can produce high-quality images, and have been developed for recording images, for example, in computer graphics.
However, conventional heat-sensitive image transfer type printing apparatuses have the problem that the transferred image is adversely affected to a small extent by extremely fine (dot-shaped) distortions and in particular the transferred colored image is degraded.
The inventors made extensive studies and experiments in order to find out the causes of distortion of the transferred images and have determined that the distortions are caused by extremely fine dust particles or the like attached to the record sheets. That is, when dust particles or the like are attached to the surface of a record sheet, they adversely affect the adhesion of dyes transferred to the record sheet, causing distortions in the transferred image. It therefore follows that the inventors believe that in order to improve the image quality, it is essential to remove all the dust particles or the like attached to a record sheet prior to the printing process.
Therefore, in order to prevent the attachment of dust particles or the like to the record sheets, the record sheet manufacturers strictly control the production of record sheets so that record sheets which are free from dust particles or the like and which are air-tightly sealed are delivered to the users. Even when the users receive such record sheets free from dust particles or the like, when a package containing record sheets is opened and the record sheets are loaded into a record-sheet feed cassette, the dust particles tend to attach to the surfaces of the record sheets. Furthermore, when the record sheets are loaded into the cassette, the fingerprints of the operator are left on the surfaces of the record sheets. Moreover, in general, the record-sheet feed cassettes have open top surfaces so that the dust particles tend to enter the cassette and attach to the surfaces of the record sheets.